In a known conventional control device including a load sensing circuit, a maximum load pressure of a plurality of actuators connected to a circuit system is selected, whereupon a regulator controls a discharge flow of a main pump such that a differential pressure between the selected maximum load pressure and a discharge pressure of the main pump remains constant. Further, an operation valve and a pressure compensation valve are connected to each actuator, and control is performed such that a supply flow remains constant regardless of variation in the load pressure of the actuators (see JP2004-197825A).